Systems and methods for forming short-fiber films, composites comprising thermosets, and other composites

ABSTRACT

The present disclosure generally relates to systems and methods for composites, including short-fiber films and other composites. In certain aspects, composites comprising a plurality of aligned fibers are provided. The fibers may be substantially aligned, and may be present at relatively high densities within the composite. For example, the composite may include substantially aligned carbon fibers embedded within a thermoplastic substrate. The composites may be prepared, in some aspects, by dispersing fibers by neutralizing the electrostatic interactions between the fibers, for example using aqueous liquids containing the fibers that are able to neutralize the electrostatic interactions that typically occur between the fibers. The liquids may be applied to a substrate, and the fibers may be aligned using techniques such as shear flow and/or magnetism. Other aspects are generally directed to methods of using such composites, kits including such composites, or the like.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/872,686, filed Jul. 10, 2019, entitled “Systemsand Methods for Short-Fiber Films and Other Composites,” and of U.S.Provisional Patent Application Ser. No. 62/938,265, filed Nov. 20, 2019,entitled “Methods and Systems for Forming Composites ComprisingThermosets.” Each of these is incorporated herein by reference in itsentirety.

FIELD

The present disclosure generally relates to systems and methods forcomposites, including short-fiber films, composites comprisingthermosets, and other composites. The present disclosure also generallyrelates to methods and systems for forming such composites.

BACKGROUND

Conventional carbon fiber composites feature planar assemblies of longcarbon fibers. In some composites, the long carbon fibers are woven intomulti-axial fabrics or uni-directional tapes. The long carbon fiberassemblies are then immersed with a polymer resin to form a compositelayer that can be laminated with other composite layers to form acomponent. Since carbon fiber is a brittle material, strong curvaturesor sharp angles in components can cause the long carbon fibers to break.Broken fibers introduce defects and compromises mechanical properties.Requiring the continuity of long carbon fibers to avoid the loss ofperformance is a limitation of conventional carbon fiber composites.

This issue can be mitigated by making composite layers with short (<5mm) carbon fibers instead of long carbon fibers. Short carbon fibers caneasily slide to drape and form around strong curvatures or sharp angles,unlike long carbon fibers. Randomly oriented short carbon fibers can beused for components that have lower performance requirements. Forcomponents with high mechanical property requirements, the short carbonfibers need to be highly oriented to approach the performance of a longcarbon fiber composite. Highly oriented short carbon fibers can also beused to drastically enhance the Z-axis mechanical properties of carbonfiber composites when they are oriented in the Z-axis. In all cases,high fiber volumes (>45%) with uniform dispersion of the short carbonfibers is required in the composite. However, there are no commerciallyavailable methods to produce short carbon fiber composites with highfiber volume content while maintaining dispersion or alignment of theshort fibers. Thus, improvements are needed.

SUMMARY

The present disclosure generally relates to systems and methods forcomposites, including short-fiber films and other composites. Thesubject matter of the present disclosure involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In one aspect, the present disclosure is generally directed to anarticle. In some embodiments, the article comprises a compositecomprising a substrate and a plurality of discontinuous fibers containedwithin at least a portion of the substrate. In some cases, the pluralityof discontinuous fibers is substantially aligned at a fiber volumefraction of at least 30 vol % within the entire composite.

The present disclosure, in another aspect, is generally directed to amethod. According to one set of embodiments, the method comprisesapplying a liquid on a substrate, where the liquid comprises a pluralityof discontinuous fibers, to cause alignment, via shear flow, of at leastsome of the plurality of discontinuous fibers, applying a magnetic fieldto the liquid to cause alignment of at least some of the plurality ofdiscontinuous fibers, and removing the liquid to form a fiber-containingsubstrate.

In another set of embodiments, the method comprises applying a liquid ona substrate, wherein the liquid comprises a plurality of discontinuousfibers; applying a magnetic field to the liquid to cause alignment of atleast some of the plurality of discontinuous fibers and/or applying ashearing fluid to the substrate to cause alignment, via shear flow, ofat least some of the plurality of discontinuous fibers; and removing theliquid to form a fiber-containing substrate.

In another aspect, the present disclosure encompasses methods of makingone or more of the embodiments described herein, for example,short-fiber films and other composites. In still another aspect, thepresent disclosure encompasses methods of using one or more of theembodiments described herein, for example, short-fiber films and othercomposites.

The present disclosure also generally relates to composites in someembodiments, including composites comprising thermosets, and methods andsystems for forming such composites.

For example, one aspect is generally directed to a composite comprisinga thermoset polymer and a plurality of discontinuous fibers containedwithin at least a portion of the composite. In some embodiments, theplurality of discontinuous fibers is substantially aligned at a fibervolume fraction of at least 20 vol % within the entire composite.

Another aspect is generally directed to a method. In one set ofembodiments, the method comprises coating at least a portion of asubstrate comprising discontinuous fibers with a thermoset polymerprecursor, curing the thermoset polymer precursor to form a thermosetpolymer, and removing at least some of the thermoset polymer from thesubstrate as a polymeric layer. In some embodiments, the discontinuousfibers are substantially aligned and are present at a volume fraction ofat least 20 vol % of the substrate.

The method, in another set of embodiments, is generally directed tocoating at least a portion of a substrate with a slurry comprising waterand discontinuous fibers, aligning at least some of the discontinuousfibers, removing water from the slurry to produce the substratecomprising the substantially aligned discontinuous fibers; coating atleast a portion of the substrate with a thermoset polymer precursor;curing the thermoset polymer precursor to form a thermoset polymer; andremoving at least some of the thermoset polymer from the substrate as apolymeric layer.

According to yet another set of embodiments, the method comprisescoating at least a portion of a substrate with a slurry comprising waterand discontinuous fibers, aligning at least some of the discontinuousfibers, coating at least a portion of the substrate with a thermosetpolymer precursor, curing the thermoset polymer precursor to form athermoset polymer, and removing at least some of the thermoset polymerfrom the substrate as a polymeric layer.

In another aspect, the present disclosure encompasses methods of makingone or more of the embodiments described herein. In still anotheraspect, the present disclosure encompasses methods of using one or moreof the embodiments described herein.

Other advantages and novel features of the present disclosure willbecome apparent from the following detailed description of variousnon-limiting embodiments of the disclosure when considered inconjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present disclosure will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the disclosure shown where illustration is not necessaryto allow those of ordinary skill in the art to understand thedisclosure. In the figures:

FIG. 1 illustrates a substrate with aligned carbon fibers, in accordancewith one embodiment of the disclosure;

FIG. 2 illustrates a composite with aligned carbon fibers, in anotherembodiment of the disclosure; and

FIG. 3 illustrates an SEM of a composite in accordance with oneembodiment.

DETAILED DESCRIPTION

The present disclosure generally relates to systems and methods forcomposites, including short-fiber films and other composites. In certainaspects, composites comprising a plurality of aligned fibers areprovided. The fibers may be substantially aligned, and may be present atrelatively high densities within the composite. For example, thecomposite may include substantially aligned carbon fibers embeddedwithin a thermoplastic substrate. The composites may be prepared, insome aspects, by dispersing fibers by neutralizing the electrostaticinteractions between the fibers, for example using aqueous liquidscontaining the fibers that are able to neutralize the electrostaticinteractions that typically occur between the fibers. The liquids may beapplied to a substrate, and the fibers may be aligned using techniquessuch as shear flow and/or magnetism. Other aspects are generallydirected to methods of using such composites, kits including suchcomposites, or the like.

The present disclosure also generally relates to composites, includingcomposites comprising thermosets, and methods and systems for formingsuch composites. Certain aspects, for example, are directed to methodsof transferring aligned fibers (e.g., carbon fibers) using a polymersuch as a thermoset polymer (e.g., an epoxy). In some cases, the polymermay be coated onto a substrate comprising fibers, and pressed and/orheated to melt or cure at least some of the polymer. The polymer canthen be removed from the substrate for example, to produce a thermosetmaterial comprising the aligned fibers. The fibers may be aligned usingtechniques such as shear flow and/or magnetism. Other aspects aregenerally directed to methods of using such composites, kits includingsuch composites, or the like.

Accordingly, certain aspects are generally directed to composites foruse in various applications. For example, for components with highmechanical property requirements, certain embodiments are generallydirected to composites comprising short fibers (e.g., less than 5 mm inlength), which may comprise carbon or other types of fibers. The fibersmay be highly oriented or aligned within the composite, which may allowit to approach the performance of a long carbon fiber composite. Highlyoriented fibers can also be used to drastically enhance the Z-axismechanical properties of the composites when they are oriented relativeto the Z-axis. In some cases, high fiber volumes (>45%) with uniformdispersion of the fibers may be used within the composite.

Certain embodiments are accordingly directed to systems and methods toproduce fiber composites with high fiber volume content whilemaintaining dispersion or alignment of the fibers. For example, thefibers may be relatively short, and may comprise carbon or othermaterials. In some cases, the fibers may be homogeneously dispersed in apolymer resin or other slurry. Short fibers may have high electrostaticinteractions that promotes agglomeration, and the high viscosity ofpolymer resins can prevent consistent dispersion at higher fibervolumes. These processing defects thus can cause inconsistent fiberreinforcement and gradients in resin content in the composite, which candrastically reduce the performance of the composite. Accordingly,certain embodiments as discussed herein can overcome these limitations.In addition, some embodiments are generally directed to aligned fibersthat maintain high fiber volume content. Apart from issues withdispersing the short fibers, prior art methods struggle with issues suchas low fiber volume fractions, insufficient alignment, or long overallfiber lengths that risk issues with fiber breaking.

Thus certain embodiments as discussed herein are directed to systems andmethods for dispersing fibers by neutralizing the electrostaticinteractions between the fibers, for example using aqueous slurries. Insome cases, the slurries containing well-dispersed fibers can be meteredonto substrates such as thermoplastic films. During metering, thealignment of the fibers can be controlled, for example, by using shearflow and/or magnetic alignment. This may be implemented, for example, ina roll-to-roll manufacturing process.

For instance, in one set of embodiments, an aqueous liquid comprisingsuitable fibers may be applied to a substrate, e.g., as a coating. Theliquid may be selected to neutralize electrostatic interactions thattypically occur between the fibers, as noted above. The substrate canbe, for example, a thermoplastic film, or other materials such asdiscussed herein. The fibers may include carbon fibers and/or otherfibers. The fibers are then aligned, for example, by applying a magneticfield and/or a shear force, e.g., by applying a suitable fluid to theliquid applied to the substrate. After alignment, the final compositemay be formed, for example, by applying heat (e.g., to remove theliquid, for example, via evaporation), and/or pressure (e.g., to embedthe fibers into the substrate).

The above discussion is a non-limiting example of one embodiment thatcan be used to produce certain types of short-fiber composite. However,other embodiments are also possible. Accordingly, more generally,various aspects are directed to various systems and methods forproducing short-fiber films and other composites and materials.

For example, certain aspects are generally directed to short-fiber filmsand other composites. In some cases, such composites may comprise asubstrate and a plurality of discontinuous or short fibers contained orembedded within the substrate, or at least a portion thereof. In somecases, the plurality of fibers are substantially aligned or orientedwithin the substrate.

A variety of materials may be used for the substrate. For instance, inone set of embodiments, the substrate comprises a polymer, such as athermoplastic or a thermoset. In some cases, the substrate consistsessentially of a polymer. In some embodiments, at least 30%, at least40%, at least 50%, at least 50%, at least 70%, at least 80%, at least90%, at least 95%, at least 97%, or at least 99% by volume of thesubstrate (without the discontinuous fibers) may be a polymer.

The substrate may include one or more polymers, including the followingpolymers, and may also include other polymers, in addition to or insteadof these polymers. Examples of suitable polymers for the substrateinclude, but are not limited to, polyimide (PI), polyamide-imide (PAI),polyetheretherketone (PEEK), polyetherketone (PEK), polyphenylesulfone(PPSU), polyethersulfone (PES), polyetherimide (PEI), polysulfone (PSU),polyphenylene sulfide (PPS), polyvinylidene fluoride (PVDF),polytetrafluoroethylene (PTFE), perfluoroalkoxy alkanes (PFA), polyamide46 (PA46), polyamide 66 (PA66), polyamide 12 (PA12), polyamide 11(PA11), polyamide 6 (PA6), polyamide 6.6 (PA6.6), polyamide 6.6/6(PA6.6/6), amorphous polyamide (PA6-3-T), polyethylene terephthalate(PET), polyphthalamide (PPA), liquid crystal polymer (LCP),polycarbonate (PC), polybutylene terephthalate (PBT), polyoxymethylene(POM), polyphenyl ether (PPE), polymethyl methacrylate (PMMA),polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE),acrylonitrile styrene acrylate (ASA), styrene acrylonitrile (SAN),acrylonitrile butadiene styrene (ABS), polybenzimidazole (PBI),polyvinyl chloride (PVC), poly-para-phenylene-copolymer (PPP),polyacrylonitrile, polyethylenimine, polyetherketonetherketoneketone(PEKEKK), ethylene tetrafluoroethylene (ETFE),polychlorotrifluoroethylene (PCTFE), and/or polymethylpentene (PMP).

The present disclosure also generally relates to composites, includingcomposites comprising thermosets, and methods and systems for formingsuch composites. Certain aspects, for example, are directed to methodsof transferring aligned fibers (e.g., carbon fibers) using a polymersuch as a thermoset polymer (e.g., an epoxy). In some cases, the polymermay be coated onto a substrate comprising fibers, and pressed and/orheated to melt or cure at least some of the polymer. The polymer canthen be removed from the substrate for example, to produce a thermosetmaterial comprising the aligned fibers. The fibers may be aligned usingtechniques such as shear flow and/or magnetism. Other aspects aregenerally directed to methods of using such composites, kits includingsuch composites, or the like.

Some aspects are generally directed to techniques for producing fibercomposites (for example, comprising carbon or other fibers) with highfiber volume content while maintaining dispersion or alignment of thefibers. Certain embodiments are generally directed to dispersing thefibers in a polymer resin, e.g., substantially homogeneously. Somefibers have relatively high electrostatic interactions that can promoteagglomeration. In addition, in some cases, some polymer resins haverelatively high viscosities that may prevent consistent dispersion athigher fiber volumes. These processing defects can cause inconsistentfiber reinforcement and gradients in resin content in the composite,which can drastically reduce the performance of the composite. Inaddition, some embodiments are generally directed to aligning fiberswhile maintaining high fiber volume content.

For example, in some embodiments, carbon and/or other fibers aredispersed by neutralizing the electrostatic interactions between thefibers in an aqueous slurry. A slurry with the dispersed fibers ismetered onto a substrate, e.g., as a coating. The alignment of thefibers can be controlled, for example, by using shear and/or magneticalignment, etc. After alignment, the fibers are infused with a thermosetresin, such as an epoxy. In some cases, this process can be implementedinto a roll-to-roll manufacturing process that allows the production offiber composites with relatively high fiber volumes and relativelywell-controlled dispersion and alignment of the fibers.

In some embodiments, a substrate may be coated with a slurry or otherliquid comprising discontinuous fibers. For example, the substrate maybe a polymer, such as polyetherimide. The slurry may be based on wateror other liquids. The discontinuous fibers may include carbon fibers,and/or other natural or synthetic fibers such as those described herein.The fibers may then be aligned using a variety of techniques, such asexposure to magnetic fields, liquids (e.g., for shear alignment), or thelike. In some cases, the fibers may be exposed to magnetic particles tofacilitate magnetic alignment, although in other cases, no magneticparticles may be used, even for magnetic alignment applications.

After alignment, some or all of the water (and/or other liquid) may beremoved from the slurry, e.g., to produce a material comprising thealigned fibers. It will be understood that practically, the alignment ofthe fibers need not be perfect, i.e., not all of the fibers may beperfectly parallel to each other. A variety of techniques may be used toremove at least some of the water and/or other liquid, such as heatingor evaporation, physical drainage, etc.

The fibers may be then be coated or otherwise exposed to a thermosetpolymer. The thermoset polymer may include an epoxy, and/or otherpolymers such as those described herein. In some cases, a film or layerof thermoset polymer may be contacted with the fibers, and in somecases, heat and/or pressure added to improve contact. For example, insome embodiments, heat and/or pressure may be added to cause at leastsome of the thermoset polymer to melt, e.g., to flow between the fibers.The thermoset polymer may then cure or harden in place, e.g., viacooling.

The hardened thermoset polymer may then be removed from the substrate,e.g., to produce a thermoset polymer comprising at least some of thefibers. In some cases, the thermoset polymer may partially or completelyembed some or all of the fibers. A variety of techniques may be used toremove the polymer from the substrate. For instance, in one embodiment,some or all of the thermoset polymer may be peeled off of the substrate,e.g., as a single polymeric layer.

The above discussion is a non-limiting example of one embodiment of thepresent disclosure that can be used to produce certain types ofshort-fiber composites. However, other embodiments are also possible.Accordingly, more generally, various aspects are directed to varioussystems and methods for producing short-fiber films and other compositesand materials.

One aspect is generally directed to composites comprising a polymericmaterial and a plurality of discontinuous fibers. The polymeric materialmay comprise a thermoset polymer. In certain cases, some or all of thediscontinuous fibers are partially or fully embedded within thethermoset polymer, or at least a portion thereof In some cases, theplurality of fibers are substantially aligned or oriented within thematerial.

In one set of embodiments, the polymeric material comprises a thermosetpolymer. In some cases, the material consists essentially of a polymer.In certain embodiments, at least 30%, at least 40%, at least 50%, atleast 50%, at least 70%, at least 80%, at least 90%, at least 95%, atleast 97%, or at least 99% by volume of the material (without thediscontinuous fibers) may be a polymer, such as a thermoset polymer.

In some embodiments, the thermoset polymer may be cured by heat and/orpressure, substantially irreversibly, from a soft solid or viscousliquid prepolymer or resin into a hardened polymer. In some cases,catalysts may be used to promote polymerization or cross-linking.

One example of a thermoset polymer is an epoxy. In some cases the epoxyresins may be reacted (e.g., cross-linked) with themselves throughcatalytic homopolymerisation, and/or with a wide range of co-reactantsincluding polyfunctional amines, acids (and acid anhydrides), phenols,alcohols and thiols (usually called mercaptans). These co-reactants areoften referred to as hardeners or curatives, and the cross-linkingreaction is commonly referred to as curing.

Other examples of thermoset polymers include, but are not limited to,polyesters, polyurethanes, bakelite, duroplast, urea-formaldehyde,melamine, diallyl-phthalates, benzoxazines, polyimides, bismaleimides,cyanate esters, polycyanurates, furan resins, silicone resins,thiolytes, vinyl esters, and the like. Additional non-limiting examplesinclude polyethylenimine, polyetherketoneketone, polyaryletherketone,polyether ether ketone, polyphenylene sulfide, polyethyleneterephthalate, a polycarbonates, poly(methyl methacrylate),acrylonitrile butadiene styrene, polyacrylonitrile, polypropylene,polyethylene, nylon, polyvinylidene fluoride, phenolics, bismaleimides,cyanate esters, polyimides, a silicone rubber, styrene butadiene rubber,or a pre-ceramic monomer, such as a siloxane, a silazane, or acarbosilane. Many such thermoset polymers and precursors thereof can beobtained commercially.

In some instances, the thermoset polymer may comprise a relatively largeportion of the polymeric material. For example, in certain embodiments,the thermoset polymer may comprise at least 1%, at least 2%, at least3%, at least 4%, at least 5%, at least 7%, at least 10%, at least 15%,at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, atleast 45%, at least 50%, at least 55%, at least 60%, at least 65%, atleast 70%, at least 75%, at least 80%, at least 85%, at least 90%, atleast 95%, or at least 97% of the mass of the material. In some cases,the thermoset polymer comprise no more than 97%, no more than 95%, nomore than 90%, no more than 85%, no more than 80%, no more than 70%, nomore than 60%, no more than 50%, no more than 40%, no more than 30%, nomore than 20%, or no more than 10% of the mass of the material.Combinations of any of these are also possible.

The material may also include additional polymers in certainembodiments, including the following polymers, and may also includeother polymers, in addition to or instead of these polymers. Examples ofsuitable polymers for the material include, but are not limited to,polyimide (PI), polyamide-imide (PAI), polyetheretherketone (PEEK),polyetherketone (PEK), polyphenylesulfone (PPSU), polyethersulfone(PES), polyetherimide (PEI), polysulfone (PSU), polyphenylene sulfide(PPS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE),perfluoroalkoxy alkanes (PFA), polyamide 46 (PA46), polyamide 66 (PA66),polyamide 12 (PA12), polyamide 11 (PA11), polyamide 6 (PA6), polyamide6.6 (PA6.6), polyamide 6.6/6 (PA6.6/6), amorphous polyamide (PA6-3-T),polyethylene terephthalate (PET), polyphthalamide (PPA), liquid crystalpolymer (LCP), polycarbonate (PC), polybutylene terephthalate (PBT),polyoxymethylene (POM), polyphenyl ether (PPE), polymethyl methacrylate(PMMA), polypropylene (PP), polyethylene (PE), high density polyethylene(HDPE), acrylonitrile styrene acrylate (ASA), styrene acrylonitrile(SAN), acrylonitrile butadiene styrene (ABS), polybenzimidazole (PBI),polyvinyl chloride (PVC), poly-para-phenylene-copolymer (PPP),polyacrylonitrile, polyethylenimine, polyetherketonetherketoneketone(PEKEKK), ethylene tetrafluoroethylene (ETFE),polychlorotrifluoroethylene (PCTFE), and/or polymethylpentene (PMP).

Certain embodiments are generally directed to composites comprisingsubstrates formed from continuous fibers, and containing a plurality ofdiscontinuous fibers. The continuous fibers generally have a length thaton average is substantially longer than the cross-sectional dimension ofthe discontinuous fibers. For instance, the continuous fibers may havean average length that is greater than 10, greater than 30, greater than50, greater than 100, greater than 300, greater than 500, or greaterthan 1,000 times the cross-sectional dimension of the discontinuousfibers. In some embodiments, the continuous fibers have an averageaspect ratio (e.g., of length to diameter or average cross-sectionaldimension) of at least 3, at least 5, at least 10, at least 30, at least50, at least 100, at least 300, at least 500, at least 1,000, etc.Additionally, in certain cases, the continuous fibers may have anaverage length of at least 5 mm, at least 1 cm, at least 3 cm, at least5 cm, or at least 10 cm. Longer average lengths are also possible insome instances.

The continuous fibers may be woven together (e.g. bidirectional,multidirectional, quasi-isotropic, etc.), and/or non-woven (e.g.,unidirectional, veil, mat, etc.). In certain embodiments, at least someof the continuous fibers are substantially parallel, and/or orthogonallyoriented relative to each other, although other configurations ofcontinuous fibers are also possible. In certain embodiments, thecontinuous fibers may together define a fabric or other substrate, e.g.,a textile, a tow, a filament, a yarn, a strand, or the like. In somecases, the substrate may have one orthogonal dimension that issubstantially less than the other orthogonal dimensions (i.e., thesubstrate may have a thickness).

The continuous fibers forming the substrate may comprise any of a widevariety of materials, and one type or more than one type of fiber may bepresent within the substrate. Non-limiting examples include carbon,basalt, silicon carbide, aramid, zirconia, nylon, boron, alumina,silica, borosilicate, mullite, cotton, or any other natural or syntheticfibers.

The continuous fibers may have any suitable average diameter. Forexample, the continuous fibers may have an average diameter of at least10 micrometers, at least 20 micrometers, at least 30 micrometers, atleast 50 micrometers, at least 100 micrometers, at least 200micrometers, at least 300 micrometers, at least 500 micrometers, atleast 1 mm, at least 2 mm, at least 3 mm, at least 5 mm, at least 1 cm,at least 2 cm, at least 3 cm, at least 5 cm, at least 10 cm, etc. Incertain embodiments, the continuous fibers may have an average diameterof no more than 10 cm, no more than 5 cm, no more than 3 cm, no morethan 2 cm, no more than 1 cm, no more than 5 mm, no more than 3 mm, nomore than 2 mm, no more than 1 mm, no more than 500 micrometers, no morethan 300 micrometers, no more than 200 micrometers, no more than 100micrometers, no more than 50 micrometers, no more than 30 micrometers,no more than 20 micrometers, no more than 10 micrometers, etc.Combinations of any of these are also possible. For example, thecontinuous fibers may have an average diameter of between 10 micrometersand 100 micrometers, between 50 micrometers and 500 micrometers, between100 micrometers and 5 mm, etc.

The continuous fibers may also have any suitable average length. Forexample, the continuous fibers may have an average length of at leastabout 0.5 cm, at least 1 cm, at least 2 cm, at least 3 cm, at least 5cm, at least 10 cm, etc. In certain embodiments, the continuous fibersmay have an average diameter of no more than 10 cm, no more than 5 cm,no more than 3 cm, no more than 2 cm, no more than 1 cm, no more than0.5 cm, or the like. Combinations of any of these are also possible; forexample, the continuous fibers may have an average length of between 1cm and 10 cm, between 10 cm and 100 cm, etc.

In some instances, the continuous fibers may comprise a relatively largeportion of the composite. For example, in certain embodiments, thecontinuous fibers may comprise at least 1%, at least 2%, at least 3%, atleast 4%, at least 5%, at least 7%, at least 10%, at least 15%, at least20%, at least 25%, at least 30%, at least 35%, at least 40%, at least45%, at least 50%, at least 55%, at least 60%, at least 65%, at least70%, at least 75%, at least 80%, at least 85%, at least 90%, at least95%, or at least 97% of the mass or volume of the composite. In somecases, the continuous fibers comprise no more than 97%, no more than95%, no more than 90%, no more than 85%, no more than 80%, no more than70%, no more than 60%, no more than 50%, no more than 40%, no more than30%, no more than 20%, or no more than 10% of the mass or volume of thecomposite. Combinations of any of these are also possible.

The composite may also contain one or more discontinuous fibers in oneset of embodiments. These may be present anywhere in the composite, forexample, contained or embedded within the substrate, or at least aportion thereof, e.g., within a polymer such as a thermoset polymer. Insome cases, the discontinuous fibers may be substantially aligned withinthe composite, e.g., forming a layer within the composite. In somecases, at least 50%, at least 70%, at least 80%, at least 90%, at least95%, at least 97%, or at least 99% by volume of the substrate maycontain discontinuous fibers. As another example, at least 50%, at least70%, at least 80%, at least 90%, at least 95%, at least 97%, or at least99% by volume of the polymeric material may contain discontinuousfibers. The discontinuous fibers may be formed or include any of a widevariety of materials, and one or more than one type of material may bepresent. For example, the discontinuous fibers may comprise materialssuch as carbon (e.g., carbon fibers), basalt, silicon carbide, siliconnitride, aramid, zirconia, nylon, boron, alumina, silica, borosilicate,mullite, nitride, boron nitride, graphite, glass, a polymer (includingany of those described herein), or the like. The discontinuous fibersmay include any natural and/or any synthetic material, and may bemagnetic and/or non-magnetic.

The discontinuous fibers, in some embodiments, may be at leastsubstantially aligned within the composite. Methods for aligningdiscontinuous fibers are discussed in more detail herein. Variousalignments are possible, and in some cases, can be determined opticallyor microscopically, e.g. Thus, in some cases, the alignment may bedetermined qualitatively. However, it should be understood that thealignment need not be perfect. In some cases, at least 5%, at least 10%,at least 25%, at least 50%, at least 75%, at least 85%, at least 90%, orat least 95% of the fibers within a substrate or composite may exhibitan alignment that is within 20°, within 15°, within 10°, or within 5° ofthe average alignment of the plurality of the fibers, e.g., within asample of the substrate or composite. In some cases, the averagealignment of the fibers may be oriented to be at least 60°, at least65°, at least 70°, at least 75°, at least 85°, or at least 87° relativeto the plane of the substrate or composite at that location.

Without wishing to be bound by any theory, it is believed that alignmentof the discontinuous fibers substantially orthogonal to the substratemay serve to provide reinforcement of the substrate or composite. Thismay improve the strength of the substrate or composite, e.g., whensubjected to forces in different directions. For instance, fibers withinthe substrate may run in substantially orthogonal directions in 3dimensions, thereby providing strength to the substrate or compositeregardless of the direction of force that is applied. The fibers mayalso limit degradation of the surface, e.g., with interlaminarmicro-cracks, through-ply fissures, or the like. In addition, in someembodiments, the fibers may enhance other properties of the substrate orcomposite, e.g., electrical and/or thermal properties within thecomposite, in addition to or instead of its mechanical properties.

While others have suggested packing fibers in a substrate or composite,it is believed that higher fiber volume fractions were previouslyunachievable, e.g., due to higher electrostatic interactions that causefiber agglomeration, and/or higher viscosities of polymer resins thatcan prevent consistent dispersion. Accordingly, certain embodiments aregenerally directed to fiber volume fractions (e.g., of substantiallyaligned fibers such as those discussed herein) of at least 40% fibervolume, at least 45% fiber volume, at least 50% fiber volume, at least55% fiber volume, at least 60% fiber volume, at least 65% fiber volume,at least 70% fiber volume, etc.

A variety of techniques may be used to align the discontinuous fibers invarious embodiments, including magnetic fields, shear flow, or the like,as are discussed in more detail below. As a non-limiting example,magnetic particles, including those discussed herein, can be attached tothe fibers, and a magnetic field may then be used to manipulate themagnetic particles. For instance, the magnetic field may be used to movethe magnetic particles into the substrate or a composite, and/or toalign the discontinuous fibers within the substrate or composite. Themagnetic field may be constant or time-varying (e.g., oscillating), forinstance, as is discussed herein. For example, an applied magnetic fieldmay have a frequency of 1 Hz to 500 Hz and an amplitude of 0.01 T to 10T. Other examples of magnetic fields are described in more detail below.

In some cases, the discontinuous fibers may have an average length, orcharacteristic dimension, of at least 1 nm, at least 3 nm, at least 5nm, at least 10 nm, at least 30 nm, at least 50 nm, at least 100 nm, atleast 300 nm, at least 500 nm, at least 1 micrometer, at least 3micrometers, at least 5 micrometers, at least 10 micrometers, at least20 micrometers, at least 30 micrometers, at least 50 micrometers, atleast 100 micrometers, at least 200 micrometers, at least 300micrometers, at least 500 micrometers, at least 1 mm, at least 2 mm, atleast 3 mm, at least 5 mm, at least 10 mm, at least 15 mm, #etc. Incertain embodiments, the discontinuous fibers may have an averagelength, or characteristic dimension, of no more than 5 cm, no more than3 cm, no more than 2 cm, no more than 1.5 cm, no more than 1 cm, no morethan 5 mm, no more than 3 mm, no more than 2 mm, no more than 1 mm, nomore than 500 micrometers, no more than 300 micrometers, no more than200 micrometers, no more than 100 micrometers, no more than 50micrometers, no more than 30 micrometers, no more than 20 micrometers,no more than 10 micrometers, no more than 5 micrometers, no more than 3micrometers, no more than 1 micrometers, no more than 500 nm, no morethan 300 nm, no more than 100 nm, no more than 50 nm, no more than 30nm, no more than 10 nm, no more than 5 nm, etc. Combinations of any ofthese are also possible. For example, the discontinuous fibers within acomposite may have an average length of between 1 mm and 5 mm.

In addition, the discontinuous fibers may also have any suitable averagediameter. For instance, the discontinuous fibers may have an averagediameter of at least 10 micrometers, at least 20 micrometers, at least30 micrometers, at least 50 micrometers, at least 100 micrometers, atleast 200 micrometers, at least 300 micrometers, at least 500micrometers, at least 1 mm, at least 2 mm, at least 3 mm, at least 5 mm,at least 1 cm, at least 2 cm, at least 3 cm, at least 5 cm, at least 10cm, etc. In certain embodiments, the discontinuous fibers may have anaverage diameter of no more than 10 cm, no more than 5 cm, no more than3 cm, no more than 2 cm, no more than 1 cm, no more than 5 mm, no morethan 3 mm, no more than 2 mm, no more than 1 mm, no more than 500micrometers, no more than 300 micrometers, no more than 200 micrometers,no more than 100 micrometers, no more than 50 micrometers, no more than30 micrometers, no more than 20 micrometers, no more than 10micrometers, etc. Combinations of any of these are also possible. Forexample, the discontinuous fibers may have an average diameter ofbetween 10 micrometers and 100 micrometers, between 50 micrometers and500 micrometers, between 100 micrometers and 5 mm, etc.

In certain embodiments, the discontinuous fibers may have a length thatis at least 10 times or at least 50 times its thickness or diameter, onaverage. In some cases, the fibers within a composite may have anaverage aspect ratio (ratio of fiber length to diameter or thickness) ofat least 3, at least 5, at least 10, at least 30, at least 50, at least100, at least 300, at least 500, at least 1,000, at least 3,000, atleast 5,000, at least 10,000, at least 30,000, at least 50,000, or atleast 100,000. In some cases, the average aspect ratio may be less than100,000, less than 50,000, less than 30,000, less than 10,000, less than5,000, less than 3,000, less than 1,000, less than 500, less than 300,less than 100, less than 50, less than 30, less than 10, less than 5,etc. Combinations of any of these are also possible in some cases; forinstance, the aspect ratio may be between 5, and 100,000.

In some instances, the discontinuous fibers may comprise a relativelylarge portion of the composite. For example, in certain embodiments, thediscontinuous fibers may comprise at least 1%, at least 2%, at least 3%,at least 4%, at least 5%, at least 7%, at least 10%, at least 15%, atleast 20%, at least 25%, at least 30%, at least 35%, at least 40%, atleast 45%, at least 50%, at least 55%, at least 60%, at least 65%, atleast 70%, at least 75%, at least 80%, at least 85%, at least 90%, atleast 95%, or at least 97% of the mass of the composite or polymericmaterial. In some cases, the discontinuous fibers comprise no more than97%, no more than 95%, no more than 90%, no more than 85%, no more than80%, no more than 70%, no more than 60%, no more than 50%, no more than40%, no more than 30%, no more than 20%, or no more than 10% of the massof the composite or polymeric material. Combinations of any of these arealso possible.

At least some of the discontinuous fibers may be uncoated. In somecases, however, some or all of the discontinuous fibers may be coated.The coating may be used, for example, to facilitate the adsorption orbinding of particles, such as magnetic particles, onto the fibers, orfor other reasons.

As one example, at least some of the discontinuous fibers are coatedwith sizing. Some examples of sizings include, but are not limited to,polypropylene, polyurethane, polyamide, phenoxy, polyimide, epoxy, orthe like. These sizings can be introduced into the slurry, for example,as a solution, dispersion, emulsion, etc. As other examples, the fibersmay be coated with a surfactant, a silane coupling agent, an epoxy,glycerine, polyurethane, an organometallic coupling agent, or the like.Non-limiting examples of surfactants include oleic acid, sodium dodecylsulfate, sodium lauryl sulfate, etc. Non-limiting examples of silanecoupling agents include amino-, benzylamino-, chloropropyl-, disulfide-,epoxy-, epoxy/melamine-, mercapto-, methacrylate-, tertasulfido-,ureido-, vinyl-, isocynate-, and vinyl-benzyl-amino-based silanecoupling agents. Non-limiting examples of organometallic coupling agentsinclude aryl- and vinyl-based organometallic coupling agents.

As mentioned, in one set of embodiments, at least some of thediscontinuous fibers may be carbon fibers. The carbon fibers may bealigned in a magnetic field directly or indirectly, e.g., using magneticparticles or other techniques such as those discussed herein. Forinstance, some types of carbon fibers are diamagnetic, and can bedirectly moved using an applied magnetic field. Thus, certainembodiments are directed to fibers or composites that are substantiallyfree of paramagnetic or ferromagnetic materials could still be alignedusing an external magnetic field. For example, if any paramagnetic orferromagnetic materials are present, they may form less than 5%, lessthan 1%, less than 0.5%, less than 0.3%, less than 0.1%, less than0.05%, less than 0.03%, less than 0.01%, less than 0.005%, less than0.003%, or less than 0.001% (by mass) of the material.

A variety of carbon fibers may be obtained commercially, includingdiamagnetic carbon fibers. In some cases, carbon fibers can be producedfrom polymer precursors such as polyacrylonitrile (PAN), rayon, pitch,or the like. In some cases, carbon fibers can be spun into filamentyarns, e.g., using chemical or mechanical processes to initially alignthe polymer atoms in a way to enhance the final physical properties ofthe completed carbon fibers. Precursor compositions and mechanicalprocesses used during spinning filament yarns may vary. After drawing orspinning, the polymer filament yarns can be heated to drive offnon-carbon atoms (carbonization or pyrolization), to produce finalcarbon fiber. In some embodiments, such techniques may be used toproduce carbon fiber with relatively high carbon content, e.g., at least90%, or other contents as described herein.

Non-limiting examples of carbon fibers include, for instance, pitch-and/or polymer-based (e.g. ex-PAN or ex-Rayon) variants, including thosecommercially-available. In some cases, these may includeintermediate/standard modulus (greater than 200 GPa) carbon fibers, highmodulus (greater than 300 GPa), or ultra-high modulus (greater than 500GPa) carbon fibers.

In one set of embodiments, the carbon fibers have a relatively highcarbon content. Without wishing to be bound by any theory, it isbelieved that such fibers may exhibit diamagnetic properties that allowsthem to be oriented with low-energy magnetic fields. In general,diamagnetism is the repulsion of a material to an applied magnetic fieldby generation of an induced magnetic field that is opposite in directionto the applied magnetic field. A material is typically categorized asdiamagnetic if it lacks noticeable paramagnetic or ferromagnetcontributions to the overall magnetic response. In many cases, themagnetic response of diamagnetic materials is very weak and negligible.However, relatively high magnetic fields can induce a noticeablephysical response in such diamagnetic materials.

Thus, in some cases, carbon fibers exhibiting relatively highly-orientedmolecular structures may exhibit anisotropic, high-diamagnetismdiamagnetic properties. Such diamagnetic properties may allow them to beoriented with relatively weak magnetic fields, such as is describedherein. For example, in one set of embodiments, an applied magneticfield may generate a strong induced magnetic field in the C—C bonds of acarbon fiber in the opposite direction of the applied magnetic field.Certain types of carbon fibers may possess a high degree of C—C bondsparallel to the in-fiber direction, which may create an anisotropicdiamagnetic response. Thus, such carbon fibers can be subjected to amagnetic torque that is neutralized when the carbon fiber alignsfully-parallel to the applied magnetic field. Accordingly, by applying asuitable magnetic field, the carbon fibers may be aligned due to suchdiamagnetic properties. This response may be sufficient to overcomegravitational, viscous, and/or interparticle steric effects.

For instance, in certain embodiments, the carbon fibers may have acarbon content of greater than 80%, greater than 90%, greater than 92%,greater than 94%, greater than 95%, greater than 96%, greater than 97%,greater than 98% greater than 99%, or greater than 99.5% by mass. Suchcarbon fibers may be obtained commercially in some cases. For example,the carbon fibers may be produced pyrolytically e.g., by “burning” oroxidizing other components that can be removed (e.g., by turning into agas), leaving behind a carbon fiber with a relatively high carboncontent. Other methods of making carbon fibers are also possible, e.g.,as discussed in detail herein.

The carbon fibers may also exhibit substantial alignment of the C-Cbonds within the carbon fibers in some instances. For instance, at least50%, at least 60%, at least 70%, at least 75%, at least 80%, at least85%, at least 90%, or at least 95% of the carbon fibers may exhibitsubstantial alignment of the C-C bonds. Such alignment may bedetermined, for example, using wide angle x-ray diffraction (WAXD), orother techniques known to those of ordinary skill in the art.

In one set of embodiments, the carbon fibers may have a relatively highmodulus (tensile modulus, which is a measure of stiffness). Typically,higher modulus fibers are stiffer and lighter than low modulus fibers.Carbon fibers typically have a higher modulus when force is appliedparallel to the fibers, i.e., the carbon fibers are anisotropic. In someembodiments, the carbon fibers may have a modulus (e.g., when force isapplied parallel to the fibers) of at least 100 GPa, at least 200 GPa,at least 300 GPa, at least 400 GPa, at least 500 GPa, at least 600 GPa,at least 700 GPa, etc. It is believed that more flexible carbon fibersmay exhibit less alignment, i.e., carbon fibers having a low modulus mayhave subtle physical responses to magnetic fields, or have no response,rather than align within an applied magnetic field.

In one set of embodiments, the carbon fibers may exhibit an anisotropicdiamagnetic response when free-floating within a liquid (e.g., water,oil, polymer resin, polymer melt, metal melt, an alcohol such asethanol, or another volatile organic compound), and a magnetic field isapplied. For example, in some cases, the carbon fibers may align when asuitable magnetic field is applied, i.e., indicative of a diamagneticresponse. In some cases, the magnetic field may be at least 100 mT, atleast 200 mT, at least 300 mT, at least 500 mT, at least 750 mT, atleast 1 T, at least 1.5 T, at least 2 T, at least 3 T, at least 4 T, atleast 5 T, at least 10 T, etc. In some cases, at least 30%, at least40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least90%, of the free-floating carbon fibers within the liquid may exhibitalignment when a suitable magnetic field is applied.

Typically, a carbon fiber has a shape such that one orthogonal dimension(e.g., its length) is substantially greater than its other twoorthogonal dimensions (e.g., its width or thickness). The fiber may besubstantially cylindrical in some cases. As mentioned, the carbon fibersmay be relatively stiff, in some instances; however, a carbon fiber neednot be perfectly straight (e.g., its length may still be determinedalong the fiber itself, even if it is curved).

In one set of embodiments, the carbon fiber may have a dimension (e.g.,a characteristic dimension) that is substantially the same, or smaller,than the thickness of the substrate or composite. For example, at leastsome carbon fibers within a substrate or composite may have an averagelength that substantially spans the thickness of the substrate orcomposite. However, in other cases, the characteristic dimension of thecarbon fiber may be greater than the thickness.

As mentioned, in one set of embodiments, particles such as magneticparticles may be added, for example, to align the discontinuous fibers,or for other applications. The particles may be adsorbed or otherwisebound to at least some of the discontinuous fibers. In some cases, theparticles may coat some or all of the discontinuous fibers and/or thecontinuous fibers. This may be facilitated by a coating of material asdiscussed herein, although a coating is not necessarily required tofacilitate the adsorption of the particles.

If the particles are magnetic, the particles may comprise any of a widevariety of magnetically susceptible materials. For example, the magneticmaterials may comprise one or more ferromagnetic materials, e.g.,containing iron, nickel, cobalt, alnico, oxides of iron, nickel, cobalt,rare earth metals, or an alloy including two or more of these and/orother suitable ferromagnetic materials. In some cases, the magneticparticles may have a relative permeability of at least 2, at least 5, atleast 10, at least 20, at least 40, at least 100, at least 200, at least500, at least 1,000, at least 2,000, at least 5,000, or at least 10,000.

However, it should be understood that not all of the particles arenecessarily magnetic. In some cases, non-magnetic particles may be used,e.g., in addition to and/or instead of magnetic particles. Non-limitingexamples of nonmagnetic particles include glass, polymer, metal, or thelike.

The particles (if present) may be spherical or non-spherical, and may beof any suitable shape or size. The particles may be relativelymonodisperse or come in a range of sizes. In some cases, the particlesmay have a characteristic dimension, on average, of at least 10micrometers, at least 20 micrometers, at least 30 micrometers, at least50 micrometers, at least 100 micrometers, at least 200 micrometers, atleast 300 micrometers, at least 500 micrometers, at least 1 mm, at least2 mm, at least 3 mm, at least 5 mm, at least 1 cm, at least 1.5 cm, atleast 2 cm, at least 3 cm, at least 5 cm, at least 10 cm, etc. Theparticles within the composite may also have an average characteristicdimension of no more than 10 cm, no more than 5 cm, no more than 3 cm,no more than 2 cm, no more than 1.5 cm, no more than 1 cm, no more than5 mm, no more than 3 mm, no more than 2 mm, no more than 1 mm, no morethan 500 micrometers, no more than 300 micrometers, no more than 200micrometers, no more than 100 micrometers, no more than 50 micrometers,no more than 30 micrometers, no more than 20 micrometers, no more than10 micrometers, etc. Combinations of any of these are also possible. Forexample, the particles may exhibit a characteristic dimension of orbetween 100 micrometer and 1 mm, between 10 micrometer and 10micrometer, etc. The characteristic dimension of a nonspherical particlemay be taken as the diameter of a perfect sphere having the same volumeas the nonspherical particle.

In some embodiments, the particles (including magnetic and/ornon-magnetic particles) may comprise a relatively large portion of thecomposite. For example, in certain embodiments, the particles maycomprise at least 1%, at least 2%, at least 3%, at least 4%, at least5%, at least 7%, at least 10%, at least 15%, at least 20%, at least 25%,at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, atleast 55%, at least 60%, at least 65%, at least 70%, at least 75%, atleast 80%, at least 85%, at least 90%, at least 95%, or at least 97% ofthe volume of the composite. In some cases, the particles comprise nomore than 97%, no more than 95%, no more than 90%, no more than 85%, nomore than 80%, no more than 70%, no more than 60%, no more than 50%, nomore than 45%, no more than 40%, no more than 35% no more than 30%, nomore than 25%, no more than 20%, no more than 15%, no more than 10%, nomore than 7%, no more than 5%, no more than 4%, no more than 3%, no morethan 2%, or no more than 1% of the volume of the composite. Combinationsof any of these are also possible.

As discussed, one set of embodiments are generally directed tocomposites, for example, comprising a polymeric material such asdiscussed herein. In some cases, the composite is generally planar,and/or may contain more than one layer or substrate. However, it shouldbe understood that the substrate, composite, or a layer within thecomposite, need not be a mathematically-perfect planar structure(although it can be); for instance, a substrate, composite or a layermay also be deformable, curved, bent, folded, rolled, creased, or thelike. As examples, the substrate, composite or a layer may have anaverage thickness of at least about 0.1 micrometers, at least about 0.2micrometers, at least about 0.3 micrometers, at least about 0.5micrometers, at least about 1 micrometer, at least about 2 micrometers,at least about 3 micrometers, at least about 5 micrometers, at leastabout 10 micrometers, at least about 30 micrometers, at least about 50micrometers, at least about 100 micrometers, at least about 300micrometers, at least about 500 micrometers, at least about 1 mm, atleast about 2 mm, at least about 3 mm, at least about 5 mm, at leastabout 1 cm, at least about 3 cm, at least about 5 cm, at least about 10cm, at least about 30 cm, at least about 50 cm, at least about 100 cm,etc. In certain instances, the average thickness may be less than 100cm, less than 50 cm, less than 30 cm, less than 10 cm, less than 5 cm,less than 3 cm, less than 1 cm, less than 5 mm, less than 2 mm, lessthan 3 mm, less than 1 mm, less than 500 micrometers, less than 300micrometers, less than 100 micrometers, less than 50 micrometers, lessthan 30 micrometers, less than 10 micrometers, less than 5 micrometers,less than 3 micrometers, less than 1 micrometers, less than 0.5micrometers, less than 0.3 micrometers, or less than 0.1 micrometers.Combinations of any of these are also possible in certain embodiments.For instance, the average thickness may be between 0.1 and 5,000microns, between 10 and 2,000 microns, between 50 and 1,000 microns, orthe like. The thickness may be uniform or non-uniform across thesubstrate, composite, or layer. Also, the substrate, composite or layermay be rigid (e.g., as discussed herein), or may be deformable in somecases.

In one set of embodiments, a binder is also present within the compositeor polymeric material, e.g., which may be used to bind the continuousfibers and the discontinuous fibers, e.g., within the composite. Forexample, the binder may facilitate holding the discontinuous fibers inposition within the composite. However, it should be understood that thebinder is optional and not required in all cases. The binder mayinclude, for example, a thermoset, thermoplastic, and/or a vitrimer. Incertain embodiments, the binder may comprise a thermoplastic solution,thermoplastic pellets, a thermoset resin, a volatile compound such as avolatile organic compound, water, or an oil. Additional non-limitingexamples of binders include polyester, vinyl ester, polyethylenimine,polyetherketoneketone, polyaryletherketone, polyether ether ketone,polyphenylene sulfide, polyethylene terephthalate, a polycarbonates,poly(methyl methacrylate), acrylonitrile butadiene styrene,polyacrylonitrile, polypropylene, polyethylene, nylon, a siliconerubber, polyvinylidene fluoride, styrene butadiene rubber, or apre-ceramic monomer, such as a siloxane, a silazane, or a carbosilane.In some cases, a binder may comprise a covalent network polymer preparedfrom an imine-linked oligomer and an independent crosslinker comprisinga reactive moiety. Non-limiting examples of reactive moieties includeepoxy, isocyanate, bismaleimide, sulfide, polyurethane, anhydride,and/or polyester. Examples of vitrimers include, but are not limited to,epoxy resins based on diglycidyl ether of bisphenol A, aromaticpolyesters, polylactic acid (polylactide), polyhydroxyurethanes,epoxidized soybean oil with citric acid, polybutadiene, etc. The bindermay also include mixtures including any one or more of these materialsand/or other materials, in certain embodiments.

In some embodiments, the binder may comprise at least 1%, at least 2%,at least 3%, at least 4%, at least 5%, at least 7%, at least 10%, atleast 15%, at least 20%, or at least 25% of the mass of the composite,and/or no more than 25%, no more than 20%, no more than 15%, no morethan 10%, no more than 7%, no more than 5%, no more than 4%, no morethan 3%, no more than 2%, or no more than 1% of the mass of thecomposite.

Composites such as those described herein may be used in a wide varietyof applications. As non-limiting examples, composites may be used indiverse applications such as reinforcement for pressure vessels,components for wind turbines, shims used in jacking heavy structures,sporting equipment, building or construction materials, laminates orencapsulants for electronic devices, battery components, or panels forvehicles such as automobiles, aircraft, marine vehicles, or spacecraft.In some cases, the composites may be useful for eliminating or reducingstress concentrations or delamination within materials, stiffeningmaterials, eliminating or reducing surface wear, dissipating electricalshocks, transmitting electrical signals, attenuating or transmittingelectromagnetic waves, dissipating thermal shocks, eliminating orreducing thermal gradients, as components for energy storageapplications, or as components for carbon fibers or ceramic matrixes.

Another aspect is generally directed to systems and methods for makingcomposites such as those described herein. In one set of embodiments,composites can be prepared from a liquid. The liquid may be, forexample, a slurry, a solution, an emulsion, or the like. The liquid maycontain discontinuous fibers such as discussed herein, and may beapplied to a substrate. The fibers may then be aligned as discussedherein, and the liquid may be then be removed, e.g., to create afiber-containing substrate. After alignment, the final composite may beformed, for example, by applying heat (for example, to remove theliquid), and/or pressure (for example, to embed the fibers into thesubstrate), e.g., to remove the liquid and/or to cure the thermosetmaterial. In some cases, the composite can be set or hardened, e.g.,with a binder, which may be used to immobilize or fix the discontinuousagents within the substrate or composite, or within a polymericmaterial. In addition, in some cases, the composite may be removed fromthe substrate, e.g., as discussed herein. The composite may berelatively stiff or flexible in various embodiments. For instance, inone set of embodiments, the composite may be wound into a continuousroll. In some cases, a liquid, such as a slurry, may be used. The slurrymay include the discontinuous fibers and optionally, magnetic particlesor other components, e.g., to be applied to the substrate.

In one set of embodiments, the liquid is able to neutralize theelectrostatic interactions between the discontinuous fibers, for exampleusing aqueous liquids. This may be useful, for example, to allow thediscontinuous fibers to be dispersed within the liquid at relativelyhigh fiber volumes without agglomeration. In some cases, surfactantsand/or alcohols can be introduced into the slurry to reduceelectrostatic interactions between the fibers. High shear mixing andflow also may help reduce agglomeration/flocculation in certain cases.

In some embodiments, the liquid phase may include, for example, athermoplastic or a thermoset, e.g., a thermoplastic solution,thermoplastic melt, thermoset, volatile organic compound, water, or oil.Non-limiting examples of thermosets include polyethylenimine,polyetherketoneketone, polyaryletherketone, polyether ether ketone,polyphenylene sulfide, polyethylene terephthalate, a polycarbonates,poly(methyl methacrylate), acrylonitrile butadiene styrene,polyacrylonitrile, polypropylene, polyethylene, nylon, polyvinylidenefluoride, phenolics, epoxies, bismaleimides, cyanate esters, polyimides,etc. Non-limiting examples of elastomers include silicone rubber andstyrene butadiene rubber, etc. Non-limiting examples of thermoplasticsinclude epoxy, polyester, vinyl ester, polycarbonates, polyamides (e.g.,nylon, PA-6, PA-12, etc.), polyphenylene sulfide, polyetherimide,polyetheretherketone, polyetherketoneketone, etc. Non-limiting examplesof ceramic monomers include a siloxane, a silazane, or a carbosilane,etc. In some cases, for example, one or more of these may be added toassist in homogenously dispersing the discontinuous fibers within theliquid. Examples of volatile organic compounds include, but are notlimited to, isopropanol, butanol, ethanol, acetone, toluene, or xylenes.

Any suitable amount of discontinuous fiber may be present in the slurryor other liquid. For instance, at least 10%, at least 15%, at least 20%,at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, atleast 50%, at least 55%, at least 60%, at least 65%, at least 70%, atleast 75%, or at least 80% of the volume of the slurry may bediscontinuous fiber. In some cases, no more than 85%, no more than 80%,no more than 75%, no more than 70%, no more than 65%, no more than 60%,no more than 55%, no more than 50%, no more than 45%, no more than 40%,no more than 35%, no more than 30%, no more than 25%, no more than 20%,no more than 15%, or no more than 10% may be discontinuous fiber.Combinations of any of these are also possible in some cases. Forexample, a slurry or other liquid may contain between 70% and 80%,between 75% and 85%, between 50% and 90%, etc. discontinuous fiber.

For example, after preparation of the slurry or other liquid, it may beapplied to or exposed to the substrate. Any suitable method may be usedto apply the slurry or other liquid to the substrate. As non-limitingexamples, the liquid may be poured, coated, sprayed, or painted onto thesubstrate, or the substrate may be immersed partially or completelywithin the liquid. The liquid may be used to wet, coat, and/or surroundthe substrate.

A magnetic field may be applied to manipulate the discontinuous fibers,directly or indirectly, as discussed herein, according to one set ofembodiments. Any suitable magnetic field may be applied. In some cases,the magnetic field is a constant magnetic field. In other cases, themagnetic field may be time-varying; for example, the magnetic field mayoscillate or periodically change in amplitude and/or direction, e.g., tofacilitate manipulation of the discontinuous agents. The oscillation maybe sinusoidal or another repeating waveform (e.g., square wave orsawtooth). The frequency may be, for example, at least 0.1 Hz, at least0.3 Hz, at least 0.5 Hz, at least 1 Hz, at least 3 Hz, at least 5 Hz, atleast 10 Hz, at least 30 Hz, at least 50 Hz, at least 100 Hz, at least300 Hz, at least 500 Hz, etc., and/or no more than 1000 Hz, no more than500 Hz, no more than 300 Hz, no more than 100 Hz, no more than 50 Hz, nomore than 30 Hz, no more than 10 Hz, no more than 5 Hz, no more than 3Hz, etc. For example, the frequency may be between 1 Hz to 500 Hz,between 10 Hz and 30 Hz, between 50 Hz and Hz, or the like. In addition,the frequency may be held substantially constant, or the frequency mayvary in some cases.

The magnetic field, whether constant or oscillating, may have anysuitable amplitude. For example, the amplitude may be at least 0.001 T,at least 0.003 T, at least 0.005 T, at least 0.01 T, at least 0.03 T, atleast 0.05 T, at least 0.1 T, at least 0.3 T, at least 0.5 T, at least 1T, at least 3 T, at least 5 T, at least 10 T, etc. The amplitude in somecases may be no more than 20 T, no more than 10 T, no more than 5 T, nomore than 3 T, no more than 1 T, no more than 0.5 T, no more than 0.3 T,no more than 0.1 T, no more than 0.05 T, no more than 0.03 T, no morethan 0.01 T, no more than 0.005 T, no more than 0.003 T, etc. Theamplitude may also fall within any combination of these values. Forinstance, the amplitude may be between 0.01 T to 10 T, between 1 T and 3T, between 0.5 T and 1 T, or the like. The amplitude may besubstantially constant, or may vary in certain embodiments, e.g., withinany range of these values.

In some embodiments, the magnetic field direction (i.e., direction ofmaximum amplitude) may vary by +/−90°, +/−85°, +/−80°, +/−75°, +/−70°,+/−65°, +/−60°, +/−55°, +/−50°, +/−45°, +/−40°, +/−35°, +/−30°, +/−25°,+/−20°, +/−15°, +/−10°, +/−5° about a mean direction.

A variety of different devices for producing suitable magnetic fieldsmay be obtained commercially, and include permanent magnets orelectromagnets. In some cases, an oscillating magnetic may be created byattaching a magnet to a rotating disc and rotating the disc at anappropriate speed or frequency. Non-limiting examples of permanentmagnets include iron magnets, alnico magnets, rare earth magnets, or thelike.

In one set of embodiments, shear flow may be used to align or manipulatethe discontinuous fibers. For example, a shearing fluid may be appliedto the substrate to cause at least some of the plurality ofdiscontinuous agents to align, e.g., in the direction of shear flow.Examples of shearing fluids that may be used include water, or anotherliquid, such as oil, an alcohol such as ethanol, an organic solvent(e.g., such as isopropanol, butanol, ethanol, acetone, toluene, orxylenes), or the like. In certain embodiments, the shearing fluid mayhave a viscosity of at least 1 cP. In addition, in some cases, theshearing fluid may be a gas, such as air. The linear flow rate of theshearing fluid, may be, for example, at least 10 mm/min, at least 20mm/min, at least 30 mm/min, at least 50 mm/min, at least 100 mm/min, atleast 200 mm/min, at least 300 mm/min, etc.

For example, in one set of embodiments, the fibers can be added to aliquid, including alcohol, solvent, or resin, to form a slurry. Theslurry can be flowed to align the fibers in some cases, e.g., whereinthe slurry is used as a shearing fluid. In other cases, however, theslurry may first be applied to a substrate, then a shearing fluid usedto align the fibers.

In addition, in some embodiments, mechanical vibration may be used tomanipulate the discontinuous fibers, e.g., in addition to and/or insteadof magnetic manipulation and/or shear flow. For example, mechanicalvibration can be used to move discontinuous fibers into or on thesubstrate, e.g., into pores or holes within the substrate, and/or atleast to substantially align the discontinuous agents within thesubstrate, e.g., as discussed herein. In one set of embodiments,mechanical vibration may be applied to cause motion of the discontinuousfibers of at least 1 micrometer, at least 2 micrometers, at least 3micrometers, at least 5 micrometers, at least 10 micrometers, at least20 micrometers, at least 30 micrometers, at least 50 micrometers, atleast 100 micrometers, at least 200 micrometers, at least 300micrometers, at least 500 micrometers, at least 1,000 micrometers, atleast 2,000 micrometers, at least 3,000 micrometers, at least 5,000micrometers, or at least 10,000 micrometers.

In addition, in some cases, the mechanical vibrations may betime-varying; for example, the mechanical vibrations may periodicallychange in amplitude and/or direction, e.g., to facilitate manipulationof the discontinuous fibers. The oscillation may be sinusoidal oranother repeating waveform (e.g., square wave or sawtooth). Thefrequency may be, for example, at least 0.1 Hz, at least 0.3 Hz, atleast 0.5 Hz, at least 1 Hz, at least 3 Hz, at least 5 Hz, at least 10Hz, at least 30 Hz, at least 50 Hz, at least 100 Hz, at least 300 Hz, atleast 500 Hz, etc., and/or no more than 1000 Hz, no more than 500 Hz, nomore than 300 Hz, no more than 100 Hz, no more than 50 Hz, no more than30 Hz, no more than 10 Hz, no more than 5 Hz, no more than 3 Hz, etc.For example, the frequency may be between 1 Hz to 500 Hz, between 10 Hzand 30 Hz, between 50 Hz and Hz, or the like. In addition, the frequencymay be held substantially constant, or the frequency may vary in somecases. If applied in conjunction with an oscillating magnetic field,their frequencies may independently be the same or different.

During and/or after alignment, the discontinuous fibers within thesubstrate may be set or fixed in some embodiments, e.g., to prevent orlimit subsequent movement of the discontinuous fibers and form arelatively hard composite, in one set of embodiments. Non-limitingexamples of techniques to form the composite include, but are notlimited to solidifying, hardening, gelling, melting, heating,evaporating, freezing, lyophilizing, or pressing the liquid or theslurry. In another set of embodiments, a material, such as athermosetting polymer, may be cured to harden the composite. Thesubstrate may thus form a composite that is a solid, a gel, or the like.

In some cases, the liquid may comprise a relatively volatile solvent,which can be removed by heating and/or evaporation (e.g., by waiting asuitable amount of time, or allowing the solvent to evaporate, e.g., ina fume hood or other ventilated area). Non-limiting examples of volatilesolvents include isopropanol, butanol, ethanol, acetone, toluene, orxylenes. Other examples of methods of removing solvents include applyingvacuum, lyophilization, mechanical shaking, or the like.

In one set of embodiments, heating may be applied to the substrate, forexample, to dry the liquid or remove a portion of the solvent, e.g., tocause the polymeric precursor to cure and/or harden. For example, thesubstrate may be heated to a temperature of at least about 30° C., atleast about 35° C., at least about 40° C., at least about 45° C., atleast about 50° C., at least about 55° C., at least about 60° C., atleast about 65° C., at least about 70° C., at least about 75° C., atleast about 80° C., at least about 90° C., at least about 100° C., atleast about 125° C., at least about 150° C., at least about 175° C., atleast about 200° C., at least about 250° C., at least about 300° C., atleast about 350° C., at least about 400° C., at least about 450° C., atleast about 500° C., etc. Any suitable method of applying heat may beused, for example, a thermoelectric transducer, an Ohmic heater, aPeltier device, a combustion heater, or the like. In some cases, theviscosity of the liquid may decrease as a result of heating. The heatingmay be applied, for example, prior, concurrent or subsequent to theapplication of magnetic field and/or mechanical vibration. In somecases, heating may be used to prevent or initiate cross-linking orcuring of a thermosetting prepolymer.

In one set of embodiments, pressure may be applied to the substrate,e.g., to partially or completely embed the discontinuous fibers into thesubstrate, e.g., to form the composite, to remove liquid, and/or toharden and/or cure a polymeric precursor to form a polymeric material,such as a thermoset material. In some cases, the pressure may be used toalso remove some of the liquid from the substrate. Examples include, butare not limited to, hot-pressing, calendaring, vacuum infusion, or thelike. The pressure, may be, for example, at least 15 psi (gauge), atleast 30 psi, at least 45 psi, etc. (1 psi=6895 Pa)

In addition, in one set of embodiments, a polymer precursor, such as aprecursor of a thermoset polymer (e.g., an epoxy), is applied to orcoated onto at least a portion of the substrate. For example, at least50%, at least 60%, at least 70%, at least 80%, at least 90%, orsubstantially all of a surface of the substrate may be coated with aprecursor. In some cases, the precursor embeds at least some of thediscontinuous fibers on the substrate, e.g., that are substantiallyaligned as discussed herein. For instance, sufficient precursor may beadded to substantially embed at least 10%, at least 20%, at least 30%,at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, atleast 90%, or substantially all of the discontinuous fibers.

The precursor may be any precursor as is described herein. For example,in one set of embodiments, the precursor is the precursor of an epoxy.The substrate may be coated or otherwise exposed to the precursor usingany suitable technique. For example, the precursor may be poured,coated, sprayed, or painted onto the substrate, or the substrate may beimmersed partially or completely within the precursor. The precursor maybe used to wet, coat, and/or surround the substrate. Other examplesinclude, but are not limited to, hot-pressing, calendaring, or vacuuminfusion.

As discussed herein the precursor may be cured and/or hardened, e.g., toform a polymer, by applying one or more suitable conditions, such asheat, pressure, catalysts, etc. Those of ordinary skill in the art willknow of suitable conditions to cause a precursor, such as a thermosetpolymer, to cure and/or harden to form a polymer. Heating and/orpressures may include any of those conditions described herein. Forexample, in some cases, the precursor may harden spontaneously, e.g.,upon evaporation of a solvent. In certain embodiments, heat may beapplied to harden the precursor, e.g., by exposing the composite totemperatures such as those described above. In some embodiments, theprecursor may be hardened upon exposure to light or a catalyst, e.g., tofacilitate or promote a chemical or polymerization reaction to cause thebinder to polymerize. For example, a thermosetting polymer may be curedupon exposure to suitable temperatures. In another example, a polymermay be exposed to ultraviolet light to cause polymerization to occur.

In some embodiments, the precursor may form a polymer comprising atleast 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least7%, at least 10%, at least 15%, at least 20%, or at least 25% of themass of the composite, and/or no more than 25%, no more than 20%, nomore than 15%, no more than 10%, no more than 7%, no more than 5%, nomore than 4%, no more than 3%, no more than 2%, or no more than 1% ofthe mass of the composite.

In some cases, after the precursor has hardened or cured to form apolymeric material, the polymeric material may optionally be removedfrom the substrate. The polymeric material may also comprise at leastsome of the discontinuous fibers from the substrate, e.g., if theprecursor was infused within or otherwise embedded or surrounded atleast some of the discontinuous fibers on the substrate. For example,the polymeric material may embed discontinuous fibers that aresubstantially aligned.

A variety of different techniques may be used to remove at least some ofthe polymer from the substrate, e.g., as a polymer material. Forinstance, in one embodiment, some or all of the thermoset polymer may bepeeled off of the substrate, e.g., as a single polymeric layer.

The polymeric material may be removed manually or automatically, forexample, by using a roll-to-roll where the material is peeled off of thesubstrate onto a roll.

A binder may also be applied in one set of embodiments, e.g., before,during, and/or after hardening of the composite and/or removal of atleast a portion of the liquid. In some embodiments, the binder may beused to produce a pre-impregnated composite ply material, e.g., bywetting dry ply material. The binder may be a liquid in some cases, andmay be caused to harden after application to the composite. In somecases, the binder is permeated into at least a portion of the composite.Non-limiting examples of permeation techniques include usinggravitational and capillary forces, by applying pressure to the binderto force it into the composite, or the like. Other examples include, butare not limited to, hot-pressing, calendaring, or vacuum infusion.However, in some cases, the binder is used to coat all, or only aportion of, the substrate, e.g., without necessarily requiringpermeation.

In some cases, the binder may comprise a resin. The binder may include athermoset or a thermoplastic. In certain embodiments, the binder maycomprise a thermoplastic solution, a thermoplastic melt, thermoplasticpellets, thermoplastic powders, thermoplastic films, a thermoset resin,a volatile compound such as a volatile organic compound, water, or anoil. Additional non-limiting examples of binders include an epoxy,polyester, vinyl ester, polyethylenimine, polyetherketoneketone,polyaryletherketone, polyether ether ketone, polyphenylene sulfide,polyethylene terephthalate, a polycarbonates, poly(methyl methacrylate),acrylonitrile butadiene styrene, polyacrylonitrile, polypropylene,polyethylene, nylon, a silicone rubber, polyvinylidene fluoride,polytetrafluoroethylene, perfluoroalkoxy alkanes, styrene butadienerubber, or a pre-ceramic monomer, such as a siloxane, a silazane, or acarbosilane. The binder may also include mixtures including any one ormore of these materials and/or other materials, in certain embodiments.

In some embodiments, the binder may comprise at least 1%, at least 2%,at least 3%, at least 4%, at least 5%, at least 7%, at least 10%, atleast 15%, at least 20%, or at least 25% of the mass of the composite,and/or no more than 25%, no more than 20%, no more than 15%, no morethan 10%, no more than 7%, no more than 5%, no more than 4%, no morethan 3%, no more than 2%, or no more than 1% of the mass of thecomposite.

After permeation, the binder may be hardened. In some cases, the bindermay harden spontaneously, e.g., upon evaporation of a solvent. Incertain embodiments, heat may be applied to harden the binder, e.g., byexposing the composite to temperatures such as those described above. Insome embodiments, the binder may be hardened upon exposure to light or acatalyst, e.g., to facilitate or promote a chemical or polymerizationreaction to cause the binder to polymerize. For example, a thermosettingpolymer may be cured upon exposure to suitable temperatures. In anotherexample, a polymer may be exposed to ultraviolet light to causepolymerization to occur.

The composite, in some cases, may contain additional layers ormaterials, e.g., in addition to these. For example, the substrate may beone of a number of layers within the composite. Other layers within thecomposite may include polymers, composite materials, metal, ceramics, orthe like. For example, the composite may be consolidated with anothercomposite layer to form a composite structure.

Composites such as those discussed herein may be used in a wide varietyof applications, in various aspects. Composites such as those describedherein may exhibit a variety of different features in variousembodiments. For example, composites such as those discussed herein maybe useful for reducing or eliminating stress concentrations, reducing oreliminating delamination, increasing planar strength and/or stiffness,reducing or eliminating surface wear, dissipating electricity (e.g., inelectrical shocks), transmitting electrical signals, attenuatingelectromagnetic waves, transmitting electromagnetic waves, dissipatingheat (e.g., in thermal shocks), reducing or eliminating thermalgradients, storing energy, synthesizing ex-PAN carbon fibers,synthesizing ceramic matrix composites (CMC), or the like.

For example, in one set of embodiments, a composite ply with at leastthree-axes of fiber orientation may be produced. This fiber structuremay allow the composite ply to distribute stresses between subsequentplies and adjacent components, which may reduce or eliminate stressconcentrations. This may significantly improve the strength of alaminated composite structure under dynamic loads, e.g., when alaminated composite structure is formed with small features or mateswith a material with drastically different stiffness (e.g. metal alloysor plastics).

Another set of embodiments is generally directed to a composite ply withthrough-plane reinforcement of the interlaminar region. This fiberreinforcement allows the composite ply to efficiently distributestresses between adjacent layers to hinder the formation of cracks andprevents a crack from propagating in the interlaminar region. Thetargeted reinforcement of the interlaminar region can significantlyimprove the strength of a laminated composite structure under shock andcyclic loads. This formulation may be useful when a laminated compositestructure is formed with long sheets of composite ply, for example,where a single crack in the interlaminar region between the plies canpotentially compromise the structural integrity of the overallstructure. Yet another set of embodiments is generally directed to acomposite ply with through-plane reinforcement, e.g., a through-planeuni-directional fabric. This fiber reinforcement may reinforce targetthrough-plane loads (e.g. point loads and high-pressure loads). Thetargeted through-plane reinforcement can significantly improve thestrength and stiffness of a laminated composite structure under expectedthrough-plane mechanical loads. This may be useful for effectivelyhandling a composite ply with through-plane reinforcement that caneasily deform during handling in an un-cured state while forming anexterior shell for a laminated composite structure.

Still another set of embodiments is generally directed to a compositeply with through-plane oriented carbon fibers. In some cases, thethrough-plane reinforcement can significantly improve the polymermatrix's resistance to damage from mechanical wear (e.g. abrasion)and/or chemical corrosion (e.g. oxidization). This formulation may beuseful, for example, for forming surfaces that protect structures frommechanical and chemical wear.

In one set of embodiments, a composite ply is provided having enhancedthrough-plane electrical conductivity. This can significantly improvethe resistance to damage caused by localized heat generation induced bycharge accumulation upon rapid discharge of electrical energy (e.g.lightning). This formulation is particularly useful for forming surfacesthat protect structures from damage from electrical discharge. Inanother set of embodiments, a composite ply with enhanced near-isotropicelectrical conductivity is provided. This may effectively conductelectrical signals. In yet another set of embodiments, a composite plyis provided with enhanced isotropic electrical conductivity. Thismaterial may effectively attenuate incident electromagnetic waves. Instill another set of embodiments, a composite ply is provide having lowradio-frequency interference and enhanced through-plane thermalconductivity to effectively transmit electromagnetic waves withoutoverheating. Another set of embodiments is generally directed to acomposite ply with enhanced through-plane thermal conductivity forsufficient structural integrity under heating. This may be useful insome embodiments for increasing structural integrity under rapidtemperature fluctuations. Still another set of embodiments is generallydirected to a composite ply with through-plane thermal conductivity andlow electrical conductivity. This formulation may be useful foreffectively moving and distributing heat flux, e.g., in electronics.

Yet another set of embodiments is generally directed to a carbon-basedcomposite ply with through-plane electrical conductivity. This may beuseful for adsorbing ionic species from an electrolyte and efficientlydistributing electrical charge.

One set of embodiments is generally directed to a composite ply withthrough-plane carbon fiber catalysts. At appropriate temperatures, a PAN(polyacrylonitrile) matrix may be oxidized and carbonized to form acarbon matrix. Another set of embodiments is generally directed to acomposite ply with through-plane carbon fiber or silicon carbidecatalysts. At appropriate temperatures, the polymer matrix may beoxidized to form a ceramic matrix.

The following documents are incorporated herein by reference: Int. Pat.Apl. Ser. No. PCT/US2018/021975, filed Mar. 12, 2018, entitled“Fiber-reinforced composites, methods therefor and articles comprisingthe same,” published as Int. Pat. Apl. Pub. No. WO 2018/175134; U.S.Patent Application Ser. No. 62/777,438, filed Dec. 10, 2018, entitled“Systems and Methods for Carbon Fiber Alignment and Fiber-ReinforcedComposites”; Int. Pat. Apl. Ser. No.: PCT/US2019/065142, filed Dec. 9,2019, entitled “Systems and Methods for Carbon Fiber Alignment andFiber-Reinforced Composites”; U.S. Provisional Patent Application Ser.No. 62/872,686, filed Jul. 10, 2019, entitled “Systems and Methods forShort-Fiber Films and Other Composites”; and U.S. Provisional PatentApplication Ser. No. 62/938,265, filed Nov. 20, 2019, entitled “Methodsand Systems for Forming Composites Comprising Thermosets.” In addition,a U.S. patent application, filed on even date herewith, entitled“Compositions and Methods for Carbon Fiber-Metal and Other Composites,”is also incorporated herein by reference in its entirety.

The following examples are intended to illustrate certain embodiments ofthe present disclosure, but do not exemplify the full scope of thedisclosure.

EXAMPLE 1

This example illustrates a slurry, comprising milled carbon fibers (highmodulus, 95% carbon content, 150 micrometers long) dispersed in water toform an aqueous slurry. This slurry was casted onto a PEI substrate (76micrometers thick), and a vertical magnetic field (0.2 T field strength,orthogonal to the PEI substrate) was applied. The vertical magneticfield oriented the milled carbon fibers as they sedimented. After thefibers were sedimented and aligned orthogonally to the PEI substrate,the water was evaporated. Once the water was removed, the PEI substratewith the vertically oriented milled fibers was compacted at 1 MPa andheated to 330° C. At this temperature and pressure, the PEI melts andthe milled fibers were embedded into the PEI melt. This material wasthen cooled to ambient temperature and the pressure released. At the endof this process, the milled fibers retained their orientation and areembedded into the PEI substrate, as can be seen in FIG. 1 .

EXAMPLE 2

The short fiber composite layer produced in Example 1 was layeredbetween two commercially available carbon fiber laminates made withcontinuous carbon fiber and PEI in this example. The layered materialwas compacted at 0.5 MPa and heated to 280° C. The PEI softened andallowed the vertically oriented milled fibers of the short fiber film topercolate with the continuous fibers of the commercially availablecarbon fiber laminates. This material was then cooled to ambienttemperature and the pressure is released, as can be seen in FIG. 2 .

EXAMPLE 3

This example illustrates a process for making a thermoset ZRT (z-axisreinforced tape), in accordance with one embodiment.

In a first step, a substrate is coated with a slurry. The substrate inthis example is an Ultem film, although other substrates may be used.The slurry contained a milled fiber dispersed in water with tracepolymer additives.

The milled fibers were next aligned by passing the coated substratethrough a vertical magnetic field of 0.3 T.

Next, water was removed from the slurry via evaporation, although someof the water was drained from the sides of the substrate. The substratewas heated to 180° C. to ensure removal of moisture. In addition, thehigh heat also “tacks up” a trace polymer binder that holds the Z-axismilled fibers in place

Next, transfer to an epoxy film was achieved by pressing a hot meltepoxy film onto the dried milled fiber coated substrate. The hot meltepoxy film was heated to 60° C. to flow the epoxy. After the epoxyflowed onto the substrate, the film was cooled and peeled from thesubstrate to produce a ZRT with a thermoset matrix. An SEM of the filmis provided in FIG. 3 .

While several embodiments of the present disclosure have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the presentdisclosure. More generally, those skilled in the art will readilyappreciate that all parameters, dimensions, materials, andconfigurations described herein are meant to be exemplary and that theactual parameters, dimensions, materials, and/or configurations willdepend upon the specific application or applications for which theteachings of the present disclosure is/are used. Those skilled in theart will recognize, or be able to ascertain using no more than routineexperimentation, many equivalents to the specific embodiments of thedisclosure described herein. It is, therefore, to be understood that theforegoing embodiments are presented by way of example only and that,within the scope of the appended claims and equivalents thereto, thedisclosure may be practiced otherwise than as specifically described andclaimed. The present disclosure is directed to each individual feature,system, article, material, kit, and/or method described herein. Inaddition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the scope of the present disclosure.

In cases where the present specification and a document incorporated byreference include conflicting and/or inconsistent disclosure, thepresent specification shall control. If two or more documentsincorporated by reference include conflicting and/or inconsistentdisclosure with respect to each other, then the document having thelater effective date shall control.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.”

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

When the word “about” is used herein in reference to a number, it shouldbe understood that still another embodiment of the disclosure includesthat number not modified by the presence of the word “about.”

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1-35. (canceled)
 36. A method, comprising: applying a liquid on asubstrate, wherein the liquid comprises a plurality of discontinuousfibers, to cause alignment, via shear flow, of at least some of theplurality of discontinuous fibers; applying a magnetic field to theliquid to cause alignment of at least some of the plurality ofdiscontinuous fibers; and removing the liquid to form a fiber-containingsubstrate.
 37. (canceled)
 38. The method of claim 36, wherein the liquidcomprises a slurry. 39-40.((canceled)
 41. The method of claim 36,wherein the liquid comprises a polymer. 42-45. (canceled)
 46. The methodof claim 36, wherein the discontinuous agents comprise carbon fibers.47. The method of claim 36, further comprising neutralizingelectrostatic interactions between the plurality of discontinuousagents.
 48. The method of claim 36, wherein the magnetic field has aminimum field strength of at least 0.01 T.
 49. (canceled)
 50. The methodof claim 36, wherein removing the liquid comprises heating the liquid toremove at least some of the liquid.
 51. The method of claim 36, furthercomprising applying pressure to the substrate.
 52. (canceled)
 53. Anarticle, comprising: a composite comprising a thermoset polymer and aplurality of discontinuous fibers contained within at least a portion ofthe composite, wherein the plurality of discontinuous fibers issubstantially aligned at a fiber volume fraction of at least 20 vol %within the entire composite. 54-58. (canceled)
 59. The article of claim53, wherein the thermoset polymer comprises an epoxy. 60-61. (canceled)62. The article of claim 53, wherein the discontinuous fibers comprisecarbon fibers. 63-80. (canceled)
 81. The article of claim 53, whereinthe composite comprises a plurality of layers.
 82. (canceled)
 83. Thearticle of claim 81, wherein a layer of the composite comprises a metal.84. The article of claim 81, wherein a layer of the composite comprisesa ceramic.
 85. A method, comprising: coating at least a portion of asubstrate comprising discontinuous fibers with a thermoset polymerprecursor, wherein the discontinuous fibers are substantially alignedand are present at a volume fraction of at least 20 vol % of thesubstrate; curing the thermoset polymer precursor to form a thermosetpolymer; and removing at least some of the thermoset polymer from thesubstrate as a polymeric layer.
 86. The method of claim 85, wherein thethermoset polymer comprises an epoxy. 87-110. (canceled)
 111. The methodof claim 85, wherein coating comprises pressing a film comprising thethermoset polymer onto the substrate.
 112. The method of claim 85,wherein curing comprises applying heat to the thermoset polymer to atemperature at least sufficient to melt at least a portion of thethermoset polymer. 113-115. (canceled)
 116. The method of claim 85,further comprising cooling the thermoset polymer after pressing the filmonto the substrate. 117-118. (canceled)
 119. The method of claim 85,wherein curing comprises applying pressure to the thermoset polymer.120-129. (canceled)
 130. The method of claim 85, wherein the substratecomprising the substantially aligned carbon fibers is prepared by:coating at least a portion of a substrate with a slurry comprising waterand the discontinuous fibers; aligning at least some of thediscontinuous fibers; and removing water from the slurry to produce thesubstrate comprising the substantially aligned carbon fibers.
 131. Themethod of claim 130, wherein aligning at least some of the discontinuousfibers comprises exposing substrate to a magnetic field having amagnetic field strength of at least 0.1 T.
 132. The method of claim 130,wherein aligning at least some of the discontinuous fibers comprisesapplying a liquid to the substrate to cause alignment, via shear flow,of at least some of the discontinuous fibers.
 133. The method of claim130, wherein the slurry comprises a polymer.
 134. The method of claim130, wherein the slurry comprises a volatile organic compound. 135-162.(canceled)